Modern computer systems typically include multiple agents each coupled to a system bus. Typically, the agents are integrated circuit packages with multiple pins coupling each agent to the bus. The agents may include, for example, processors, memory devices, mass storage devices, etc. In order for the computer system to operate properly, agents should be able to communicate effectively with each other via the bus. Because computer systems and computer system agents sometimes evolve separately, computer systems usually include agents that have different capabilities. For example, agents may be capable of transmitting and receiving different data widths. Systems such as these are typically limited to transmitting the smallest data widths of the multiple data widths the agents are capable of transmitting. Typically, this data width must be set once at initialization and cannot be changed during computer system operation. Thus, it is typically not possible to take advantage of an agent's greater capability to transmit data.
Existing computer systems typically transfer data between components or agents in accordance with a predefined clocking scheme. A system bus clock typically clocks data out of a sending device and into a receiving device. Consequently, it takes at least one complete clock cycle of a system bus clock to transfer data from one device to another device. Data can be transferred in a source synchronous fashion in order to increase the speed of data transmission. In source synchronous transmission, a strobe is sent with a data transmission. This strobe latches the data into the receiving device in a time period that is typically shorter than the period of the system bus clock. In present systems capable of source synchronous transmission, this transmission mode must be selected at initialization and cannot be changed during operation of the computer system. For this reason, agents that are not capable of source synchronous transmission prevent a system designer from taking advantage of those agents that are capable of source synchronous transmission.